A valve stem seal's fitness for use depends upon its ability to prevent fluid from passing thereby, upon its mechanical strength, and upon its antifriction properties. The adverse effects of temperature upon the valve components and frictional properties significantly affect fitness for use.
In a sealing system for the purpose of isolating fluid on one side of a seal from fluid on the other while directly transmitting mechanical force and/or torque from one side to the other, one or more seals wipe the moving member in a manner directed to isolating the fluids. This is conventionally done with mechanical wipers such as "Vee's, cones, or U-cups" with initial lubrication provided. Lubrication methods include having a compressible section of felt or braid which serves as a seal and wick for lubricant when squeezed by a packing cap or spring.
With most stem seal systems, shrinkage and lack of compliance of said materials at low temperatures result in leaks. Special materials are required at high temperatures, wherein the shrinkable/compliance problems are exacerbated at low temperatures.
Plastic materials have substantially higher yield strengths and low creep rates at lower temperatures, and hence the adaptability which contributes to sealing at higher temperatures is not readily available at lower temperatures.
The purposes of the present invention are to provide a low friction valve stem sealing arrangement in which a lubrication ring carries lubricant to the seal elements, and to provide positive lubricant installation and containment.